This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2006-074579, filed Mar. 17, 2006; and No. 2006-088976, filed Mar. 28, 2006, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a variable valve device for an internal combustion engine, which controls a valve.
2. Description of the Related Art
A reciprocating engine mounted in an automobile is an example of an internal combustion engine. In some reciprocating engines, in order to achieve better mileage, the engine can be run in a cylinder-suspension mode in which some of the cylinders are suspended under driving conditions wherein a large output is not required.
In the running in the cylinder-suspension mode, frequent lifts of inlet and exhaust valves of the cylinder are stopped with variable valve devices to decrease pumping loss. That is, opening and closing of the valve are stopped.
Unlike the inlet valve, there are few demands for the exhaust valve that a valve lift amount and open-close timing are precisely controlled according to a running state of the engine. Therefore, in order to simplify the structure of a rocker shaft for stopping the exhaust valve lift, a rocker arm incorporated into the rocker shaft is divided into a cain follower rocker which follows a cam and a valve drive rocker which drives the valve. A displacement of the cam follower rocker is transmitted to or cut off from the valve drive rocker through a switching portion (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2005-90408).
When the cam follower rocker and the valve drive rocker are connected to each other with the switching portion, the displacement of the exhaust cam is transmitted from the cam follower rocker to the exhaust valve through the valve drive rocker. When the cam follower rocker and the valve drive rocker are separated from each other by the switching portion, the cam follower rocker strikes the air for the valve drive rocker. Therefore, the displacement of the exhaust cam is not transmitted to the valve drive rocker.
Usually the two exhaust valves are tend to be used to enhance exhaust performance of the burned gas. Therefore, frequently a front-end side of an arm is branched in the valve drive rocker of the exhaust valve, and front-end portions of the branched arm are arranged in an upper end portion of the valve. This enables the two exhaust valves to be simultaneously driven (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2005-90408).
In the divided-type rocker arm structure, frequently a body is formed by casting with an iron-based metal material such as steel because strength is increased.
Because the as-prepared iron-based metal material such as the steel has difficulty in the strength, usually machining is carried out to secure accuracy after quenching is carried out as heat treatment. Specifically, because the iron-based metal material for which the quenching is carried out has high hardness, the machining is carried out on the iron-based metal material not by cutting but by polishing.
In the case where both the cam follower rocker and the valve drive rocker are made of the steel, the cam follower rocker has a portion, to which a high impact load is imposed, including a region which receives the displacements of the cam and an abutment which abuts on the piston. Therefore, from the viewpoint of strength, the use of the steel for which the quenching is carried out is required.
On the other hand, the valve drive rocker has no portion to which the high impact load is imposed. Specifically, the load imposed on the piston is received by a wide area such as a portion in which the piston is accommodated. Therefore, such high strength is not required compared with the cam follower rocker, but instead the valve drive rocker has a portion for which high accuracy is required.
In the case where the cam follower rocker and the valve drive rocker are made of the steel, as with the cam follower rocker, the quenching and the polishing are carried out even on the valve drive rocker in which the product accuracy is emphasized, which results in the problem that machining man-hours are increased, leading to higher cost in the variable valve device.
In view of the foregoing, an object of the invention is to provide a variable valve device for an internal combustion engine, in which machining man-hours can be decreased.
A variable valve device of the present invention comprises: a camshaft which is rotatably provided in an internal combustion engine while having a cam; a rocker shaft which is arranged next to the camshaft; a valve which is driven by the cam; a cam follower rocker which is rotatably provided in the rocker shaft, and is rocked by following the cam; a valve drive rocker which is rotatably provided in the rocker shaft next to the cam follower rocker, and drives the valve; and a switching portion which be able to switch the valve drive rocker between a drive state and a non-drive state. Either a body of the cam follower rocker or a body of the valve drive rocker is made of an iron-based metal material, and the other body is made of a material different from the iron-based metal material, heat treatment being not required in the different material.
According to this structure of the invention, one of the body of the cam follower rocker or the body of the valve drive rocker is made of the iron-based metal material, and the other body is made of the different material for which the heat treatment is not required. Therefore, the heat treatment and the particular machining are eliminated.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.
A first embodiment of the invention will be described with reference to
Referring to
Small components such as a head cover and an oil pan are not shown in
As shown in
Plural (for example, two) exhaust ports 14a and 14b and plural (for example, two) exhaust valves 15a and 15b are provided in the outside between the banks 7a and 7b. The exhaust valves 15a and 15b open and close the exhaust ports 14a and 14b. Therefore, combustion air is drawn from the inside of the bank, and the burned gas is exhausted from the outside of the bank. A consistently-closed structure biased toward a closed direction by a valve spring (not shown) is used in the inlet valves 13a and 13b and the exhaust valves 15a and 15b respectively.
Single overhead camshaft (SOHC) variable valve systems 17 are provided in the cylinder heads 6 of the right and left banks 7b and 7a, and the variable lift operations of the inlet and exhaust valves can be realized in SOHC variable valve systems 17.
The variable valve system 17a of left bank 7a includes an (three-mode switchable) inlet variable valve device 18 and an (two-mode switchable) exhaust variable valve device 19 (corresponding to a variable valve device of the invention). A normal (low-speed) mode, a high-speed mode, and a cylinder-suspension mode (mode for suspending the cylinder) can be switched in the inlet variable valve device 18. The normal (low-speed) mode and the cylinder-suspension mode (mode for suspending the cylinder) can be switched in the exhaust variable valve device 19.
The variable valve system 17b of the right bank 7b includes an (two-mode switchable) inlet variable valve device 20 and an exhaust variable valve device 21. The normal (low-speed) mode and high-speed mode can be switched in the inlet variable valve device 20. The exhaust variable valve device 21 has only the normal (low-speed) mode.
A structure of the one cylinder will be described below. Referring to
An oil passage 27a for the cylinder-suspension mode is formed along an axial direction in the rocker shaft 27. An oil passage 26a for the cylinder-suspension mode and an oil passage 26b for high-speed mode are formed along the axial direction in the rocker shaft 26. The oil passage 26a and the oil passage 26b are communicated with an end of the oil passage 27a.
The camshaft 25 is rotated by a crank output. As shown in
The low-speed inlet cam 33 has a cam profile in which open-close timing and a valve lift amount are set so as to be suitable for low-speed running of the engine. The high-speed inlet cam 30 has a cam profile in which open-close timing and a valve lift amount (larger than that of the low-speed cam 33) are set so as to be suitable for high-speed running of the engine in the same base circle as the low-speed inlet cam 33. The non-lift cam 31 has a cam profile (only the base circle) having the same radius. The exhaust cam 32 has a cam profile in which open-close timing and a valve lift amount are set so as to be suitable to the discharge of the combustion gas.
As shown in
For details, as shown in
As shown in
In an outer peripheral surface of the boss 36, as shown in
When the inlet valves 13a and 13b are closed, the slipper 41 is caused to abut on the non-lift cam 31 by reaction forces of the valve springs of the inlet valves 13a and 13b, which prevents accidental motion of the whole of the valve drive rocker 35.
A piston type switching operation portion is used as both the switching operation portions 40a and 40b arranged in both end portions of the boss 36. The switching operation portion 40a arranged on the side of the (low-speed) inlet cam 33 will be described below. Referring to
A piston 46 is accommodated in the cylinder 43 along with a compression spring 47 which biases the piston 46 against the bottom of the cylinder 43 (shown only in
As shown in
As with the switching operation portion 40a, a structure in which a cylinder 51 is formed in the base portion of the rocker arm 37 is used in the switching operation portion 40b arranged on the side of the (high-speed) inlet cam 30 as shown in
Unlike the switching operation portion 40a, as shown in
A low-profile piston is used as the piston 53 such that the piston 53 can be accommodated in the cylinder portion on the lower side from the window 50. Contrary to the switching operation portion 40a, usually the opening of the window 50 of the cylinder 51 is opened, and the opening is closed by the outer peripheral surface of the piston 53 when the piston 53 is raised.
A pin 55 is slidably accommodated in the through hole 52. As shown in
As shown in
As shown in
The cam follower rocker 70 includes a cylindrical rocker shaft supporting boss 71, a pair of roller support pieces 72, a roller 73, and a wing portion 74. The rocker shaft 26 located adjacent to the end of the boss 36 is rotatably fitted in the rocker shaft supporting boss 71. The roller support pieces 72 are linearly projected toward the overhead location of the (high-speed) inlet cam 30 from both end portions of the boss 71. The roller 73 is rotatably supported between the front-end portions of the roller support pieces 72. The wing portion 74 is formed in the boss 71.
The roller 73 is rotated while being in contact with the inlet cam 30. When the camshaft 25 is rotated, the cam follower rocker 70 is rotated about the boss 71, namely, the cam follower rocker 70 is rocked while following displacement of the inlet cam 30.
In order to maintain the following capability of the cam follower rocker 70, the roller 73 is pressed against the inlet cam 30 by the biasing force of a pusher 70a (partially shown by the alternate long and two dashes line in
As shown in
Specifically, the inside roller support piece 72 is arranged at the point where the roller support piece 72 is continued to the window 50 on the straight line by utilizing the shift. Therefore, the cam follower rocker 70 can be rocked while maintaining an attitude in which the inside roller support piece 72 is arranged in front of the window 50. Obviously the cut portion 57 and the cut portion 76 are formed in the sizes and shapes so as not to obstruct the motion of the cam follower rocker 70.
The wing portion 74 is formed by utilizing the roller support piece 72 arranged in front of the window 50 (shown in
The wing portion 74 is formed by hanging over the front-end portion of the rib portion 78 to the point of the window 50. An abutment 79 which can enter into and leave from the window 50 is formed in a horizontal waIl constituting the hung-over front-end portion. Usually the abutment 79 enters into and leaves from the cylinder 51 through the window 50. When the window 50 is blocked by the piston 53, the abutment 79 abuts on the piston 53 exposed from the window 50.
That is, the switching whether or not the displacement of the high-speed inlet cam 30 from the cam follower rocker 70 is input to the valve drive rocker 35 is carried out based on whether the abutment 79 constituting the front-end portion of the wing portion 74 strikes the air or abuts on the piston 53. That is, the switching operation portion 40b and the wing portion 74 constitute a switching mechanism for carrying out the above switching.
As shown in
As shown in
The switching whether or not the displacement of the low-speed inlet cam 33 from the cam follower rocker 60 is input to the valve drive rocker 35 is carried out based on whether the abutment 69 strikes the air or abuts on the piston 46. The switching operation portion 40a and the wing portion 74 constitute the switching mechanism.
As shown in
The cam follower rocker 80 includes a cylindrical rocker shaft supporting boss 81, a U-shape roller support piece 82, a roller 83, and a wing portion 84. The portion corresponding to the exhaust cam 32 in the rocker shaft 27 is rotatably fitted in the rocker shaft supporting boss 81. The roller support piece 82 is linearly projected from both end portions of the boss 81 toward the overhead location of the exhaust cam 32. The roller 83 is rotatably supported between the front-end portions of the roller support piece 82. The wing portion 84 is formed in the boss 81.
The roller 83 is rotated while being in contact with the exhaust cam 32. When the camshaft 25 is rotated, the cam follower rocker 80 is rotated about the boss 81, namely, the cam follower rocker 80 is rocked while following the displacement of the exhaust cam 25. In order to maintain the following capability of the cam follower rocker 80, the roller 83 is pressed against the exhaust cam 32 by the biasing force of a pusher 80a (partially shown by the alternate long and two dashes line in
The wing portion 84 has a rib 86 which is integrally formed in the center of the width direction in the outer surface of the boss 81. The rib 86 is extended along a circumferential direction of the boss 81 from the rear end portion of the roller support piece 82 to the upper portion of the boss 81. An abutment 89 is provided in the front-end portion of the rib 86, and the abutment 89 is formed by the horizontal wall hung over toward the forward direction.
As shown in
A pair of cylindrical rocker shaft supporting bosses 92 are provided in one end portion of the rocker arms 91. The rocker shaft 27 on both sides where the boss 81 (cam follower rocker 80) is located therebetween in the rocker shaft 27 are rotatably fitted in The rocker shaft supporting bosses 92.
Arms 93 are provided in the other end portion of the rocker arms 91, and the arms 93 are linearly extended from the bosses 92 to the exhaust valves 15a and 15b respectively. One arm 93 is next to the another arm 93. Adjustment screws 94 are provided on the front-end portions of the respective arms 93. The adjustment screws 94 are arranged at upper ends (valve stem ends) of the exhaust valves 15a and 15b respectively.
The arms 93 are connected by a plate-shape connecting arm 95 (corresponding to the connecting arm of the invention) at the end portions of the arms 93, specifically, at the points where the adjustment screws 94 exist. Therefore, the pair of rocker arms 91 are integral with each other. That is, when the valve drive rocker 90 is rocked about the rocker shaft 27, the valve drive rocker 90 drives the exhaust valves 15a and 15b.
In an outer peripheral surface of the boss 96, as shown in
When the exhaust valves 15a and 15b are closed, the slipper 96 is caused to abut on the non-lift cam 31 by the reaction forces of the valve springs of the exhaust valves 15a and 15b, which prevents the accidental motion of the whole of the rocker arm 91.
As shown in
The switching operation portion 98 will be described below. Referring to
A piston 102 is accommodated in the cylinder 99 along with a compression spring 103 which biases the piston 102 against the bottom of the cylinder 99. Therefore, usually the window 100 of the cylinder 99 is closed by the outer peripheral surface of the piston 102. The piston 102 is retracted from the window 100 to open the window 100 when the piston 102 is raised.
As shown in
The relay passage 106 communicates with a branch passage 107 (only shown in
The abutment 89 of the cam follower rocker 80 is positioned in front of the window 100. As shown in
That is, the switching whether or not the displacement of the exhaust cam 32 from the cam follower rocker 80 is input to the valve drive rocker 90 is carried out based on whether the abutment 89 strikes the air or abuts on the piston 102. That is, the switching operation portion 98 and the wing portion 84 constitute a switching mechanism 110 (corresponds to the switching portion of the invention).
On the other hand, as shown in
The OCVs 120 and 121 which are the two oil-pressure supply systems are connected to a control unit 122 (for example, the control unit includes a microcomputer). The control unit 122 has functions of closing the OCVs 120 and 121 in the low-speed mode, opening the OCV 121 in the high-speed mode, and opening the OCV 120 in the cylinder-suspension mode according to a map which is previously set depending on the running state of the automobile.
Such a structure is adopted as each cylinder of the left bank 7a, which enables three-stage switching of the valve drive with the high-speed inlet cam 30, the valve drive with the low-speed inlet cam 33, and the non-valve drive in the inlet system of the left bank 7a. In the exhaust system of the left bank 7a, the two-stage switching of the valve drive and the non-valve drive is carried out by the exhaust cam 32.
On the other hand, the structure, in which the mechanisms and components associated with the non-valve drive are removed from the inlet variable valve device 18 of the left bank 7a, is used as each inlet variable valve device 20 of the variable valve system 17b of the right bank 7b. Although not shown, in the structure, the low-speed-side switching structure (mainly switching operation portion 40a and cam follower rocker 60) is omitted, and the low-speed inlet cam 33 always directly drives the valve drive rocker 35. Therefore, the two-stage switching can be carried out between the low-speed mode and the high-speed mode while only the high-speed-side switching structure is left.
The structure in which the mechanisms and components associated with the non-valve drive are removed from the exhaust variable valve device 19 of the left bank 7a, i.e., the structure in which the exhaust cam 32 always directly drives only the valve drive rocker 90 is used on the exhaust side.
In the structure of the right bank 7b, the oil passages 26a and 27a for the cylinder-suspension mode are omitted, and only the oil passage 26b is left. That is, in the inlet system, the right bank 7b has the structure in which the two-stage switching is carried out between the valve drive with the high-speed inlet cam 30 and the valve drive with the low-speed inlet cam 33. In the exhaust system, the right bank 7b has the structure in which only the valve drive is carried out by the exhaust cam 32.
The running state in which parts of the cylinders (three cylinders of the left bank 7a) are suspended is carried out by the variable valve systems 17a and 17b of the right and left banks 7b and 7a.
In the variable valve devices 18, 19, and 20, bodies 60x, 70x, and 80x (the whole rocker) of the cam follower rockers 60, 70, and 80 have a portion to which a high impact load is imposed. Examples of the portion include a region which receives the displacements of the cams 30, 32, and 33 and the abutments 69, 79, and 89 which abut on the pistons 46, 53, and 102.
Therefore, the portions to which the high impact load is imposed is made of steel to which quenching is carried out to secure strength. That is, the bodies 60x, 70x, and 80x are formed by the following forming process. The bodies 60x, 70x, and 80x are formed by casting with the iron-based metal material, specifically, the steel. The strength is secured by carrying out the quenching on the casting product, and dimensional accuracy is secured by carrying out polishing on the casting product.
The valve drive rockers 35 and 90 comprise the cylinder 43, 51, and 99. The cylinder 43, 51, and 99 accommodating the piston 46, 53, and 102 are required high accuracy. High strength is not required in the cylinder 43, 51, and 99 unlike the cam follower rockers 60, 70, and 80.
The valve drive rockers 35 and 90 in which the dimensional accuracy has higher priority than the strength are made of not the iron-based metal material such as the steel for which the heat treatment is required, but a different material for which the heat treatment is not required, i.e., a non iron-based metal material.
Specifically, in the valve drive rockers 35 and 90, an aluminum material is used as the forming material. The bodies 35x and 90x (the whole except for the piston) of the valve drive rockers 35 and 90 are made of the aluminum material.
As shown in
Thus, the aluminum valve drive rockers 35 and 90 are configured. As shown in
Action of the variable valve system 17 will be described with reference to
Therefore, as shown by a solid line of
Then, on the inlet side of the left bank 7a, the (high-speed) cam follower rocker 70 is rocked while striking the air. At the same time, the (low-speed) cam follower rocker 60 is rocked while abutting on the piston 46. In the exhaust side of the left bank 7a, the cam follower rocker 80 is rocked while abutting on the piston 102.
Therefore, on the inlet side, the displacement of the (low-speed) inlet cam 33 transmitted from the cam follower rocker 60 is transmitted from the valve drive rocker 35 to the pair of inlet valves 13a and 13b through the pair of rocker arms 37, which drive the inlet valves 13a and 13b.
On the exhaust side, the displacement of the exhaust cam 32 transmitted from the cam follower rocker 80 is transmitted from the connecting arm 95 of the valve drive rocker 90 to the pair of exhaust valves 15a and 15b through the pair of arms 93 extended toward the valve end, which drives the exhaust valves 15a and 15b.
In the variable valve device 20 of the right bank 7b, as with the left bank 7a, the (high-speed) cam follower rocker strikes the air. Therefore, only the displacement of the low-speed inlet cam transmitted to the valve drive rocker is transmitted to the pair of inlet valves, which drive the inlet valves. In the variable valve device 21 on the exhaust side, the displacement of the exhaust cam is directly transmitted to the pair of exhaust valves through the pair of arms, which drive the exhaust valves by the valve drive rocker.
Therefore, the V-type engine is operated in the low-speed mode brought by the combination of the low-speed cam and the exhaust cam of
When a command for enabling the high-speed mode is sent to the control unit 122 according to the running state of the automobile, only the OCV 121 for the high-speed mode is opened by the control unit 122. That is, the oil pressure is applied only to the oil passage 26b.
Then, the oil pressure is applied to the pin 55 of the (inlet-side) switching operation portion 40b of the left bank 7a. Therefore, the piston 53 is driven upward by the pin 55, which blocks the window 50 as shown by the alternate long and two dashes line of
Then, as shown by the alternate long and two dashes line of
At this point, the window 44 of the switching operation portion 40a is blocked by the piston 46. However, because the outer shape of the high-speed inlet cam 30 is set larger than that of the low-speed inlet cam 33, only the displacement of the (high-speed) inlet cam 30 transmitted from the cam follower rocker 70 is transmitted from the valve drive rocker 35 to the pair of inlet valves 13a and 13b through the pair of rocker arms 37.
That is, the inlet valves 13a and 13b are driven by the high-speed inlet cam 30. The displacement of the exhaust cam 32 is transmitted from the cam follower rocker 80 to the connecting arm 95 of the valve drive rocker 90, which continuously drives the exhaust valves 15a and 15b.
In the variable valve device 20 of the right bank 7b, as with the left bank 7a, the displacement of the (high-speed) inlet cam transmitted from the cam follower rocker is transmitted from the valve drive rocker to the pair of inlet valves through the pair of rocker arms, which drive the inlet valves. The variable valve device 21 of the right bank 7b directly and continuously drives the pair of exhaust valves by the valve drive rocker.
Therefore, the V-type engine is operated in the high-speed mode brought by the combination of the high-speed cam and the exhaust cam of
When a command for enabling the cylinder-suspension mode is sent to the control unit 122 according to the running state of the automobile, only the OCV 120 for the cylinder-suspension mode is opened by the control unit 122, which applies the oil pressure to the oil passages 26a and 27a.
Therefore, on the inlet side of the left bank 7a, the oil pressure is applied to the pin 48 to drive the pin 48 upward, which upwardly drives the piston 46 of the switching operation portion 40a to open the window 44 as shown by the alternate long and two dashes line of
Because the oil pressure is not applied to the switching operation portion 40b, the window 50 remains opened as shown in
Therefore, in the left bank 7a, the cam follower rocker 60 (inlet: low speed), the cam follower rocker 70 (inlet: high speed), and the cam follower rocker 80 (exhaust) are rocked while striking the air, which blocks the transmission of the driving force for driving the valve to the valve drive rockers 35 and 90 (inlet and exhaust).
Accordingly, as shown in
In the left bank 7a, the separation between the cam follower rockers 60, 70, and 80 and the valve drive rockers 35 and 90 stops the lifts (open and close) of the inlet valves 13a and 13b and the exhaust valves 15a and 15b.
At this point, as with the low-speed mode, in each of the inlet variable valve device 20 and the exhaust variable valve device 21 of the right bank 7b, the displacement of the low-speed inlet cam is continuously transmitted to the inlet valve while the displacement of the exhaust cam is continuously transmitted to the exhaust valve, which switches to the cylinder-suspension mode in which parts of the cylinders (cylinders of left bank 7a) are suspended.
Thus, in the engine in which the gate-type valve drive rocker 90 is adopted on the exhaust side, even if the valve drive rocker 90 is arranged while offset toward one side (one side of the cylinder 3) between the exhaust valves 15a and 15b as shown in
Additionally, the load is imposed on the pair of arms 93 with no swing stress, when the valve drive rocker 90 is pushed down to open the exhaust valves 15a and 15b or when the valve drive rocker 90 is returned to close the exhaust valves 15a and 15b by the connection of the end portions of the arms 93 with the connecting arm 95.
Accordingly, the structure of the gate-type valve drive rocker 90 can always repeat a predetermined valve lift to improve the engine performance. Furthermore, when the switching operation portion 98 which switches the transmission between the cam follower rocker 80 and the valve drive rocker 90 is provided in the connecting arm 95, because the load from the cam follower rocker 80 is symmetrically imposed onto the exhaust valves 15a and 15b, namely, because the load is equally imposed on the exhaust valves 15a and 15b, the high reproducibility is obtained in the valve lifts.
Particularly, when the switching operation portion 98 is provided in the substantial center between the exhaust valves 15a and 15b, the even load is imposed on the exhaust valves 15a and 15b, so that the higher reproducibility is obtained.
Because the heavy switching operation portion 98 including the cylinder and the piston is provided in the connecting arm 95, the load generated by the increased weight of the switching operation portion 98 is also evenly imposed, so that the reproducibility is increased in the valve lifts.
Additionally, because a part of the switching portion is provided in the connecting portion to suppress the increase in weight, not only the friction is reduced, but also particularly the design valve lift is easily reproduced at high engine speed, which obtains high engine performance. Because the load bias is hardly generated for the switching abutment, the movement of the contact point is suppressed in the switching abutment. Therefore, the wear is suppressed in the switching region to improve the durability.
According to the variable valve devices 18, 19, and 20 which carry out the mode switching, the required strength is secured by the quenching (heat treatment) for the cam follower rockers 60, 70, and 80 (made of iron-base metal).
The valve drive rockers 35 and 90 which link with the cam follower rockers 60, 70, and 80 are made of non iron-based metal material for which the heat treatment is not required. Therefore, the valve rocker 35 and 90 are able to secure the dimensional accuracy. The same holds true for the right bank 7b.
In the valve drive rockers 35 and 90 in which the dimensional accuracy has the higher priority, unlike the cam follower rockers 60, 70, and 80, the adoption of the non iron-based metal material eliminates not only the quenching (heat treatment) but also polishing which is carried out on a region where hardness is increased by the heat treatment. That is, a near net shape is achieved in the valve drive rockers 35 and 90, thereby decreasing the machining man-hours required until the component is completed.
Accordingly, in the variable valve devices 18, 19, and 20, the production cost can be suppressed by forming the valve drive rockers 35 and 90 with the material different from the cam follower rockers 60, 70, and 80, i.e., with the non iron-based metal material. Because the valve drive rockers 35 and 90 having the pistons 46, 53, and 102 are made of the aluminum material in the non iron-based metal material, the region for which the machining is required, i.e., each portion of the cylinders 43, 51, and 99 accommodating the pistons 46, 53, and 102 is formed not only by the polishing but by other machining methods. Therefore, machinability is improved to rationally carry out the machining.
There is no risk of the heat deformation caused by the quenching in the valve drive rockers 35 and 90, so that the product is easily obtained with high accuracy. Therefore, cost reduction is further achieved in the variable valve devices 18, 19, and 20.
Even if the valve drive rockers 35 and 90 are made of the non iron-based metal material, e.g., the aluminum material for which the heat treatment is not required, the valve drive rockers 35 and 90 have the sufficient durability because the strength against the swing is enhanced in the valve drive rockers 35 and 90. As a result, the machining man-hours are reduced for the valve drive rocker 90.
The load imposed on each piston becomes substantially equal by the symmetric arrangement of the cam follower rockers. Therefore, because the wear of the cylinder is suppressed, the valve drive rockers 35 and 90 have the sufficient durability, even if the valve drive rockers 35 and 90 are made of the non iron-based metal material, e.g., the aluminum material for which the heat treatment is not required. In the case where the cam follower rockers are not symmetrically arranged, the large load is imposed on one of the cylinders, which causes the cylinder to be easily worn.
Alternatively, as shown in
However, in the second embodiment, the composition having the similar function as the first embodiment is designated by the same reference numeral and the description thereof is omitted.
In the second embodiment, the same effects as the first embodiment are obtained.
Thus, when the sleeve 200 is provided, the sliding loads of the pistons 46 and 53 are mainly imposed on the sleeve 200, so that in addition to the effects obtained in the first embodiment the wear resistance is enhanced in the cylinders 43 and 51.
However, in
The sleeve 200 may be adopted in the variable valve device described in the second embodiment.
The invention is not limited to the above embodiments, but various changes and modifications could be made without departing from the scope of the invention. For example, the invention is applied to the V-type engine in the above embodiments. Alternatively, the invention may be applied to other engines, such as a straight-type engine, in which the cylinders are arranged in a different way.
Although the non-lift cam and the exhaust cam are switched in the embodiments, the invention may be applied to the switching between a small lift and a large lift including the small lift. In this case, although the load becomes imbalance during the low lift, there is generated no problem because the load is small during the low lift. The effect of the invention is similarly obtained during the high lift with the high load.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
---|---|---|---|
2006-074579 | Mar 2006 | JP | national |
2006-088976 | Mar 2006 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
5460130 | Fukuzawa et al. | Oct 1995 | A |
5845614 | Tanaka et al. | Dec 1998 | A |
7007646 | Takayasu et al. | Mar 2006 | B2 |
7107953 | Takayasu et al. | Sep 2006 | B2 |
Number | Date | Country |
---|---|---|
2005-90408 | Apr 2005 | JP |
Number | Date | Country | |
---|---|---|---|
20070215082 A1 | Sep 2007 | US |